These experiments will study the genes responsible for certain T lymphocyte-specific functions. These will include genes coding for T-cell receptors as well as for the cytolytic activity of T killer cells. A dual approach will be used to clone the respective genes. Recipient T cells will be transformed with "marked" DNA from T killer cells. Transformed cells which express the donor T cell-specific antigen receptor will be selected in a fluorescence-activated cell sorter. After multiple rounds of selection and cloning of positive cells the "marked" genes will be isolated by recombinant DNA technology. Concomitantly, a differential cDNA library will be produced from a T killer cell and used to select chromosomal genes which are expressed in a T killer cell and not in a T-cell receptornegative variant. The function of such T cell-specific DNA clones will again be tested by cell transformation. The genes isolated by both approaches will be analyzed by restriction enzyme mapping, electron microscopy and DNA sequencing to determine their structure and organization. The T-cell genes which code for the ability to kill will be isolated and analyzed in a similar way. It is hoped that the experiments will resolve the structure of the T-cell receptor and the organization of the genes coding for the receptor. Furthermore, we anticipate that the combination of cell transformation and recombinant DNA technology will open the way to elucidating the molecular and genetic basis of immune cell interactions in general.